High frequency receiver



y 193% w. SCHEPPMANN 2,043,433

HIGH FREQUENCY RECEIVER Filed Feb. 1, 1932 UNITED STATES PArEr HIGH FREQUENCY RECEIVER Wilhelm Scheppmann, Berlin-Neutempelhof,

Germany, assignor to C. Lorenz Aktiengesellschaft, Berlin-Tempelhof, Germany, a com- D y Application February 1, 1932, Serial No. 590,213 In Germany January 31, 1931 4 Claims. (Cl. 250-20) i F I Q E (Granted under the provisions of sec. 14, act of March 2, 1927; 357 O. G.

This invention relates generally to ultra short of the tube R1 serves as a reaction coil and is wave receiving systems, and it relates more parcoupled with coil L2. Condensers C1 and C2 are ticularly to a heterodyne method of ultra short adapted to tune to the desired receiving fre- Wave reception. quency. Furthermore, a coil L4, being coupled 5 The desirability of applying the heterodyne with another coil L5, is disposed in the grid cirprinciple to the reception of ultra short waves cuit of the tube R1. The coil L5 is disposed in has long been recognized, for this application the anode circuit of the tube R2. The tube R2 would permit the received high frequency waves is actuating as a heterodyne local oscillator and to be transformed into alternating current of a its grid circuit is provided with an oscillatory '19 "lower frequency, the beat frequency, which can circuit L6, C3 tuned to the heterodyne frequency,

be more efiiciently amplified. It has been found, While the anode circuit of the tube with the coil however, that the desired application is by no L5 and the condenser Cl is likewise tuned to the means easily effected because of the difficulty desired frequency. In the anode circuit of the in maintaining a constant beat frequency. This tube R1 a beat or intermediate frequency s1 is is difilculty has been caused by the fact that the produced by heterodyning the transmission frel5" oscillations emitted by the transmitter, as well quency received over the dipole to the frequency as the oscillations generated by the heterodyne produced by the heterodyne local oscillator R2, local oscillators, vary considerably at the high the beat or intermediate frequency being led to frequencies employed in ultra short wave transan intermediate frequency amplifier Z over the mission. transformer T1. 29

In order to maintain the beat frequencies cOn- The intermediate frequency amplifier Z is of stant, heterodyne local oscillators controlled by a well known construction. For this purpose all quartz crystal oscillators have been employed. customary types of intermediate frequency am- Receivers of this kind, however, being very costly plifiers, be it with transformer or resistance couand having a very critical adjustment point, are pling, etc., may be used. An amplifier according 25 unsuitable for general use. to Fig. 1, for instance, may be used wherein in According to e p e t v ti heterodyne the input of the first tube R3 a choke filter 05, L7, methods can be applied to the reception of ultra C6, L8 and a condenser filter L9, C7, L10, C8 are short Waves without the use of quartz crystal employed. In the anode circuit of the tube R4 30 oscillators to control the heterodyne local oscilis disposed a circuit S1 tuned to the intermediate lators. frequency and coupled with a circuit S2 Which This result is accomplished by employing means is likewise tuned to the intermediate frequency for maintaining the oscillations of the local hetand disposed in the grid circuit of a second tube ro yn o illa or a n an as possible, and R4. The anode circuit of this second tube is then h n pr vi ng means Which permit the quency connected to the transformer T2, the secondary of the oscillations emitted by the transmitter, as winding of which i connected ith th 1 frewell as the frequency of the oscillations generquency section N, of a generally accepted type. ated by the local et dy Oscillator to Vary In the form illustrated in Fig. 1 the low frequency Within rather Wide limits and yet control a section N contains a detector R5 upon the input 40 ceiver. of which intermediate frequency from transform- AI]. embodiment Of thG invention is shown by er T2 i impressed The low frequency signa de- W 9 example in the accompanying drawing, tected in the detector R5 is impressed through In Whlch transformer T3 upon the input of an amplifier Rs 1 luustrates schematlcany the clrcwts of which amplifies the detected signal and impresses the embodiment; and th e E renderi the r c 'V dsi Fig. 2 is a diagram illustrating the range of fi ggfi i r mg 6 e1 8 g permitted frequency variations.

i t r is sgiggg g gi i' ggi i gi 1 :3 as nearly constant as possible, it is desirable to Tpossesses a coil L1 which is coupled with the coil heat the filaments the tubes and R2 L2 of a receiver. The receiver is provided with rectly rather t an directly, for 1t 15 well known a tube R1 which is connected as an audion valve that, QWlng to'the thermal l e O an nullfor the ultra-short Wave reception, and has th rectly heated filament, the emission of a tube hav-" coil L2 connected in the grid circuit thereof. n a fi a e Of this yp is influenced to a lesser In order to maintain the intermediate frequency 'ECoil L3 which is connected in the anode circuit degree by fluctuations in the heating of its fila- 55.

ment than is the emission of a tube having a directly heated filament.

The potentiometer G, which is of the glow discharge tube type, is a further means for maintaining the frequency of the tubes R1 and R2 constant. Since the frequency generated by each 01' these tubes depends largely upon their anode potential, it is essential to keep this potential constant which is done by means of the potentiometer G. Since potentiometers of this type are well known in the art, it is regarded as unnecessary to describe its operation in detail here.

Despite the indirect heating of the filament in the tubes R1 and R2 and the use of the potentiometer G to control the anode potential in these tubes, there is necessarily some variation in the intermediate frequency 2/ impressed upon the intermediate frequency amplifier Z. This variation is caused by variations in the frequencies of the signals received by the antenna D and residual variations in the frequencies of the oscillations generated by the local oscillator 2. These frequency variations result from the ultra high frequencies of the transmitted signals and of the locally generated oscillations, respectively.

The variations of the intermediate frequency, however, have no effect upon reception provided they are Within certain limits, for the intermediate frequency amplifier Z includes, among its circuit elements, one or more band pass filters which are so designed that the total amplification of this amplifier is substantially the same for a wide band of frequencies, as indicated at B in Fig. 2. The amplifier Z may also include several stages of amplification for the purpose of intensifying the intermediate frequency a).

Referring to Fig. 2, S represents the transmission band of the distant transmitter; the continuous curve in S represents the relative amplitude of the intermediate carrier frequency in and the side bands thereof; and, as before stated, B represents the transmission band or frequency range f1 to f2 of the band pass filter or filters in the intermediate frequency amplifier Z. The intermediate carrier frequency In lies within the range ii to 2 which is so chosen that the signalling band S composed of the intermediate frequency carrier f with the upper and lower side bands, may shift its position, to some extent, and still be within the transmission range f1 to f2 of the intermediate frequency amplifier. Usually the width of the signalling band S, when both side bands are transmitted, is not more than 20,000 cycles with a modulating signal composed of frequencies up to 10,000. t should be noted that the transmission band of the band pass filters is a multiple of the transmission band of the distant transmitter, and may be of any selected width. For example, in the case of a transmitter modulated in a normal manner, the band pass filters of the intermediate frequency amplifier Z may have a transmission band of 100,000 cycles per second. It is evident from Fig. 2 that considerable variations in the frequency band of the transmitter (not shown) and in the frequency of the oscillations generated by the tube R2 may occur, yet, so long as the resultant intermediate or beat frequency zf varies within the limits of B, the total amplification of the intermediate frequency amplifier Z remains substantially the same.

Hence, if the oscillations of the receiver tubes R1 and R2 are maintained as nearly constant as possible by indirectly heating the filaments of these tubes and associating a potentiometer of the glow discharge type with the anodes thereof, and the transmission band of the intermediate frequency amplifier Z is made sufficiently broad to pass the beat or intermediate frequency despite any fluctuations in the oscillations generated by the transmitter (not shown) and by the tube R2, then ultra short waves may be detected and received in a most reliable manner without the use of a quartz crystal oscillator for controlling the local oscillator at the receiver.

It is to be understood that the invention is not restricted to arrangements for separate local oscillators such as R2, but may be also employed with self heterodyne local oscillators. It is evident, also, that modifications of the invention may be made within the scope indicated by the appended claims without departing from the spirit of the invention.

What is claimed is:

l. The method of ultrashort wave reception which comprises receiving transmitted modulated ultrashort waves of variable frequency, combining locally generated oscillations of variable frequency with the carrier frequency of the received waves to produce an intermediate frequency, conducting the intermediate frequency through a path having an intermediate frequency transmission band equal to a multiple of the transmitted frequency band, and utilizing the intermediate frequency so conducted to produce a signal.

2. In a high frequency receiver, an antenna for receiving ultrashort waves, an ultrashort wave detector tube associated with said antenna and having an anode and an indirectly heated filament, a local oscillator tube also having an anode and an indirectly heated filament, a glow discharge potentiometer for controlling the anode potential of said tubes, means for impressing said locally produced oscillations upon said detector tube for interaction thereon with the received oscillations to produce an intermediate frequency, and a receiving circuit for the intermediate frequency, said receiving circuit having an intermediate transmission frequency band equal to a multiple of the frequency band of the ultrashort waves received by said antenna.

3. In a high frequency receiver, an antenna for receiving ultrashort waves, an ultrashort wave detector associated with said antenna and having an anode and an indirectly heated filament, a local oscillator also having an anode and an indirectly heated filament, a glow discharge potentiometer for controlling the anode potential of said detector and oscillator, means for impressing said locally produced oscillations upon said detector tube for interaction thereon with the received oscillations to produce an intermediate frequency, an amplifier for the intermediate frequency, means whereby the total amplification of said amplifier is substantially the same for a wide band of frequencies, and receiving means associated with the output of said amplifier.

4. In a high frequency superheterodyne receiver, the combination of a first detector and a heating frequency oscillation generator employing tubes of the indirectly heated type, each tube having a plate circuit, means coupling the oscillator to the detector for impressing thereon the generated oscillations, a source of current for the plate circuits of said tubes, a glow discharge potentiometer connected in parallel with said source, and leads from said potentiometer to the plates of said tubes.

WILHELM SCHEPPMANN. 

